1. Technical Field
This invention relates to a delivery system for an implantable medical member. More particularly, the invention relates to a delivery system including a tapered dilator having a splittable portion at each of the proximal and distal ends of the dilator.
2. Background Information
Delivery devices, such as guide catheters and introducer sheaths, are widely used in the medical field as conduits for percutaneously transporting an implantable medical device through the vasculature of a patient to a target site for deployment.
Often the delivery device having the medical device positioned therein must traverse tortuous passageways in the patient's vasculature to reach the desired deployment site. A variety of introducer or delivery sheaths have been developed in an attempt to optimize this process. For example, some sheaths are formed to have different hardness levels, or durometers, along the length of the sheath. Such sheaths may have a high durometer at the proximal end, one or more intermediate sections of increasingly lower durometer, and a distal section having the lowest durometer. This arrangement enables the distal portion of the sheath to more easily bend while traversing increasingly narrow and tortuous passageways, while maintaining a higher degree of strength and rigidity at the proximal end.
Sheaths may be formed with a layered structure, which structure may include the presence of a reinforcing layer. One type of reinforcement is a helical coil that is disposed between inner and outer polymeric layers of the sheath. The presence of the coil enables the sheath to bend as it encounters a bending stress, and then return to its original orientation upon release of the stress. This type of reinforcement is also generally effective for resisting bulging of the sheath adjacent to the self-expanding stent enclosed therein. Another type of reinforcement is a woven braid. A braided reinforcement enhances the torqueability of the sheath as it traverses the passageway. Sheaths may be formed to combine one or more features of the aforementioned designs, as well as other features that may be added for a particular purpose.
Regardless of the particular construction of the introducer device, the introducer is typically housed within a passageway of a tapered dilator for introduction into a body passageway. The tapered dilator facilitates passage through tortuous passageways within the body. Once this delivery system comprising the dilator and the introducer sheath reaches the target site, it is desirable to remove the dilator from the introducer sheath prior to deployment of the medical device. Removal of the dilator from the introducer can be problematic, and many prior art attempts have been made to facilitate such removal. One such attempt comprises providing a dilator having a frangible distal tip. With this design, the dilator can be peeled away from the introducer sheath upon splitting of the tapered distal tip of the dilator. Although this apparatus works well in some instances, it performs less so in other instances. One such instance involves removal of the dilator from an implantable device having a large proximal end (e.g., a pacemaker lead). The presence of the large proximal end impedes peeling away of a sheath that has been split only at the distal end.
It is desired to provide a delivery system for use in delivering an implantable medical device to a target site within the body of a patient, and wherein the dilator is more easily removed from around the introducer when compared to existing systems.